Infiltration Characteristics of Carbon Fiber Reinforced MMCs

Abstract

Carbon fiber reinforced aluminum matrix composite blocks and a pipe (as semi-product) were produced by pressure infiltration technique. In this paper the authors deal with the production method and investigations of the blocks and the pipe. In our composites AlSi12 eutectic aluminium-silicon alloy was used as matrix material. The reinforcements were ‘A’ and ‘B’ type carbon fibers (‘A’ having lower amorphous carbon content than ‘B’). The volume fraction of the fibers was outstanding – at least 55 vol%. Scanning electron microscopic investigations were done in order to observe the rather rough surface of the carbon fibres. X-ray diffraction and energy dispersive spectrometry was done in order to estimate the quantity of Al4C3 intermetallic phase at the carbon fiber/matrix interface region. The measurements showed that the quantity of Al4C3 strongly depends on the amorphous carbon quantity in carbon fibers. Much more Al4C3 was formed in the case of ‘A’ type reinforcement (less amorphous carbon), than in the case of ‘B’ type reinforcement (more amorphous carbon). The presence of Al4C3 crystals caused large scatter in the mechanical properties, the UTS was decreased, while the compressive strength was increased. Fracture surfaces were investigated: the composite showed rigid fracture.